IMGT®, the international ImMunoGeneTics information system®, was created in 1989 as a high-quality integrated knowledge resource specialized in immunoglobulins (IG), T cell receptors (TR), major histocompatibility complexes (MHC) of human and other vertebrates, and related proteins of the immune system (RPI) which belong to the immunoglobulin superfamily (IgSF) and to the MHC superfamily (MhcSF). IMGT® is the international reference in immunogenetics and immunoinformatics. IMGT® combines sequence databases (IMGT/LIGM-DB, IMGT/PRIMER-DB, IMGT/PROTEIN-DB, IMGT/MHC-DB), a genome database (IMGT/E-DB), and a three-dimensional (3D) structure database (IMGT/3Dstructure-DB) with interactive analysis tools (IMGT/V-QUEST, IMGT/JunctionAnalysis) and Web resources comprising 8000 HTML pages (IMGT Repertoire). The accuracy and consistency of IMGT data are based on IMGT-ONTOLOGY, available for biologists and IMGT users in the IMGT Scientific chart and for computer scientists in IMGT-ML, in XML format. IMGT® components (databases, tools, and Web resources) have been developed according to three main biological approaches: the genomic approach that is gene centered, the genetic approach that refers to genes in relation to their polymorphisms, expression, specificity, and evolution, and the structural approach that analyses 3D structures in relation to protein function and recognition sites. We are implementing Web services for the IMGT databases and tools. This is the first step toward IMGTChoreography that will trigger and coordinate dynamic interactions between IMGT Web services in order to process complex significant biological and clinical requests. IMGT® is widely used in fundamental and medical research (repertoire analysis of the IG antibody sites and of the TR recognition sites in autoimmune diseases, infectious diseases, AIDS, leukemias, lymphomas, myelomas), veterinary research situations (IG and TR repertoires in farm and wildlife species), genome diversity and genome evolution studies of the adaptive immune responses, biotechnology related to antibody engineering (single chain Fragment variable (scFv), phage displays, combinatorial libraries, chimeric, humanized, and human antibodies), diagnostics (clonalities, detection and follow-up of residual diseases), and therapeutical approaches (graft, immunotherapy, vaccinology). IMGT® is freely available at http://imgt.cines.fr. [ABSTRACT FROM AUTHOR]